Compressed Air Rocket
When one molecule of air hits another molecule in an object, the air molecule bounces off, producing a tiny, tiny push. When many, many air molecules hit something, all the little pushes together create one very large push. This is called air pressure.
Any time there is air, there will be pressure, because the molecules are always zooming around and bumping into things. We don’t usually notice the pressure from the all around us because it’s pushing in on us from every direction and we are used to it.
But what happens if we take some air, and give it less space to move around in? Let’s find out – by building a rocket!
What you need:
- 1 empty squeeze bottle with a flat cap
- 1 small coffee straw
- 1 drinking straw
- Glue
- Scissors
- Colored Paper
What you do:
- Have an adult help you punch or drill a hole in the top of the cap of the plastic bottle.
- Push the smaller straw through the hole about half an inch and glue the joints shut. This is the launching pad.
- Cut the drinking straw to about four or five inches long and seal one end shut with glue. This will be your rocket.
- Cut four small paper triangles and attach them to the opposite end of the straw as rocket fins.
- Slide the drinking straw over the smaller straw until the end of the smaller straw barely touches the glued-shut head of the rocket. Squeeze the bottle hard and watch your rocket fly!
What happened?
When you press the plastic bottle, the air inside is compressed. This means that there is less space between the air molecules, so they are hitting each other and the walls of the bottle much more. When the molecules hit each other more often, there is higher pressure. The air wants to escape to a place with more space between molecules so they don’t hit each other as much. That is, higher pressure air wants to go to places with lower pressure.
The air inside the bottle is at high pressure when the bottle is squeezed, and it needs to escape. The only way for it to get to lower pressure like the air outside the bottle is to push the rocket off.
That’s right – air pressure causes a push. Air pressure on an object causes a force.
Experiment with different kinds of heads and fins of your rocket
to see which kinds fly the farthest. The IMSA on Wheels team got
their rocket to fly seven meters – can you beat us?
IMSA on Wheels - IMSA Kids Institute - Illinois Mathematics and Science Academy
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